DE102008044214B4 - Method for adjusting a braking system in a vehicle - Google Patents

Abstract

Method for adjusting a braking system in a vehicle, in which braking force is automatically generated in defined driving situations, wherein the automatic generation of braking force is aborted by a defined driver reaction, wherein the automatic generation of braking force is aborted when at least one driver reaction reaches an associated threshold value, characterized in that the reaction time, the duration, strength and/or number of a driver reaction is taken into account.

Description

The invention relates to a method for adjusting a braking system of a vehicle according to the preamble of claim 1.

State of the art

From the DE 197 53 971 A1 A method for automatically applying braking force is known in which, in the event of an impending collision situation, braking force is built up beyond the driver's specifications in order to reduce the severity of an accident or to avoid a subsequent accident. The additional braking force, which is built up automatically, brakes the vehicle to a standstill in a shorter time or keeps the vehicle at a standstill.

The automatic generation of braking force can be aborted by defined driver reactions. Such driver reactions are defined in the DE 197 53 971 A1 releasing the brake pedal or the parking brake if the vehicle speed exceeds a minimum value. The automatic build-up of braking force is also interrupted when the accelerator pedal is pressed. This is to ensure that the driver regains control of the sole operation and control of the vehicle through a conscious reaction.

However, a distinction must be made between a deliberate interruption of the autonomous generation of braking force caused by a specific driver reaction and cases in which the driver intervenes in the driving state through a conscious or unconscious reaction without, however, pursuing the intention of interrupting the build-up of braking force. This includes panic reactions by the driver and accidental activations, for example as a result of a driver movement due to the heavy braking of the vehicle.

From the printed publications EN 20 2004 058 814 A1 and EN 10 2008 010 667 A1 discloses a method for adjusting a braking system in a vehicle, in which braking force is automatically generated in defined driving situations, wherein the automatic generation of braking force is aborted by a defined driver reaction, wherein the automatic generation of braking force is aborted when at least one driver reaction reaches an associated threshold value.

Disclosure of the invention

The invention is based on the task of aborting an autonomous braking intervention in a vehicle by a conscious driver reaction. In particular, those reactions of the driver with which the driver consciously wants to regain complete control of the vehicle should be reliably detected.

This object is achieved according to the invention with the features of claim 1. The subclaims specify expedient further developments.

The method according to the invention for adjusting a braking system in a vehicle is based on a driving situation with autonomous braking force generation. This applies, for example, to driving situations in which a dangerous situation has been detected, such as an impending collision, which can be determined using environmental sensors such as radar sensors. In order to prevent an impending accident or to reduce the expected severity of the accident, braking force can be built up automatically in these situations, regardless of whether the driver operates the brake pedal.

However, in order to give the driver back control over driving the vehicle, criteria are formulated that must be met in order for the autonomous braking intervention to be aborted. According to the invention, certain driver reactions are defined for this purpose, from which it can be concluded that the driver has overruled the situation, whereupon the automatic generation of braking force is aborted. According to the invention, the abort takes place in the event that at least one driver reaction reaches an assigned threshold value.

By specifying a reaction-specific threshold value, a distinction can be made between conscious driver reactions that the driver intentionally causes to stop the automatic build-up of braking force, and those situations in which a driver reaction occurs but the driver does not want the autonomous braking intervention to be reduced. The duration, strength and/or number of driver reactions can be taken into account as the driver reaction.

In contrast to designs known from the state of the art, the specification of the threshold value allows a better distinction between the intended and the undesired driver reactions for the termination of the automatic braking force build-up by taking into account the strength or level of the driver reaction as a criterion for the termination of the autonomous braking intervention via the comparison with the threshold value.

According to a practical embodiment, the automatic braking force build-up is aborted if at least two defined driver reactions occur during the autonomous braking intervention. This can be done either with the identical driver reaction occurring, for example, at two consecutive points in time, or with different driver reactions being considered. A combination of both is also possible, i.e. taking into account the same driver reaction at different points in time during the autonomous braking intervention or taking into account different driver reactions. Even with the aforementioned different combinations of different driver reactions or the same driver reaction at different points in time, the reaction time, duration, strength and/or number of individual reactions can be taken into account by assigning the respective threshold values.

Driver reactions can be examined, for example, by operating the accelerator pedal, the brake pedal and the steering wheel. Other reactions can also be used, such as operating the parking brake or handbrake. All of the characteristics of the unit in question are to be understood as an actuation, such as the level, strength, duration of the reaction time, etc., whereby several reactions can also be derived during one actuation. Repeated actuations of a unit can also be considered separate reactions.

In principle, it is possible to take the driver reactions into account cumulatively or alternatively. For example, if only a single driver reaction is sufficient to abort the autonomous braking intervention, it is sufficient to define a plurality of different driver reactions, of which only one must reach the assigned threshold value. In a further embodiment with at least two criteria to be achieved, it is sufficient for any two driver reactions from a large number of different driver reactions to cumulatively reach the assigned threshold value.

In addition, it is also possible to make a hierarchical subdivision of the driver reactions, for example by introducing a weighting of different driver reactions in order to determine a characteristic value that represents the termination of the autonomous braking intervention. The different driver reactions can be weighted using coefficients, which is particularly relevant if a plurality of different driver reactions are taken into account. For example, different driver reactions can be linked in a linear combination to form a characteristic value that represents the termination of the automatic generation of braking force, with the coefficients achieving a desired weighting. The characteristic value represents a probability on the basis of which a decision is made as to whether the autonomous braking intervention should be terminated. If, for example, the characteristic value is greater than a probability threshold such as 0.5, the automatic generation of braking force is terminated. The linear combination of the individual driver reactions is transformed into a probability value, for example using the logistic regression method.

Furthermore, it is possible to carry out an additional verification based on other current driver actions to ensure that the driver actually has an over-determination intention. Such driver actions must be cumulative with the driver reactions, each of which must exceed an assigned threshold value. The verification action, however, does not necessarily have to reach a threshold value; rather, it is sufficient that such an action takes place regardless of the level, for example pressing the accelerator pedal as a verification action for additional, further driver reactions.

Typical driver reactions include interventions by the driver in the pedals or steering wheel, i.e. brake pedal operations, accelerator pedal operations or steering wheel operations. In the case of vehicles with manual transmissions, clutch operations or generally the operation of a hand or parking brake can also be taken into account. Furthermore, it is possible, for example, to use optical sensors to monitor the driver's movement behavior for typical behavior patterns and to derive an override intention to abort the autonomous braking intervention.

The method according to the invention for adjusting a braking system in a vehicle runs in a control device which is installed in the vehicle, in particular in a central control device of the braking system in the vehicle.

Further advantages and expedient embodiments can be found in the further claims, the description of the figures and the drawing, in which a flow diagram for carrying out the method is shown in a schematic manner.

The highly schematic block diagram represents the process for aborting an autonomous braking force intervention through a conscious driver reaction. The block diagram therefore assumes that the driving situation is such that, for example, an autonomous braking intervention is carried out due to a detected risk of collision, in which braking force is built up independently of the driver.

Blocks 1 to 3 symbolize various driver reactions during the autonomous braking intervention, which are examined in order to derive an override intention of the driver, which leads to the termination of the autonomous braking intervention. In the example, only three different blocks 1 to 3 are shown for different driver reactions, although in principle any number or different driver reactions can be taken into account.

When the accelerator pedal is operated, the number of individual operations during the autonomous braking intervention is taken into account, as well as the duration of each operation, the reaction time until the operation and the height of the operation. In addition, first and second derivatives of the accelerator pedal operation can also be taken into account, i.e. the pedal speed and the pedal acceleration, both when the accelerator pedal is pressed down and when the accelerator pedal is released.

For example, it is useful to take into account the number of kickdown operations, with the probability that the driver intends to override increasing as the number increases. Accordingly, this criterion is assigned a threshold value of preferably greater than 1. Furthermore, the reaction time until the first kickdown can be taken into account, with a negative correlation in this case, so that the probability of an override intention increases the shorter the reaction time. Furthermore, the length of time for which the first kickdown is held can be taken into account, with the intention to override increasing as the duration increases.

It is also possible to take into account full throttle operations, which by definition are below the kickdown operation, whereby in this case too the number, reaction time and duration of the full throttle operation can be taken into account, but preferably with different threshold values than the kickdown operations. It is also possible to take into account the duration of a second full throttle operation, whereby the distinction between individual full throttle or kickdown operations or generally between individual accelerator pedal operations is made in such a way that the driver at least slightly, but possibly also completely, releases the accelerator pedal position.

Even below the threshold of full throttle operation, the accelerator pedal position can be used to determine the driver's override intention. In particular, the maximum accelerator pedal position during the intervention period is considered, with the override intention increasing with the increase in the accelerator pedal position.

Another criterion that can be taken into account is the integration in the mathematical sense of the accelerator pedal position, whereby the intention to override increases with an increasing value of the integral. The duration of the first accelerator pedal actuation during the autonomous braking intervention can also be taken into account, whereby in this case too an increasing duration indicates a greater intention to override.

Another criterion to be considered is the maximum accelerator pedal speed, both when increasing the accelerator pedal position and when releasing the accelerator pedal, whereby a high pedal speed when depressing the pedal indicates a high override intention, whereas a lower pedal speed when releasing the accelerator pedal indicates a higher probability of the override intention.

The absolute accelerator pedal acceleration can also be taken into account, particularly when the accelerator pedal position is increased, whereby the override intention also increases with increasing accelerator pedal acceleration. If necessary, the accelerator pedal acceleration when the accelerator pedal is released is also taken into account.

Another driver reaction that can be considered is the actuation of the brake pedal, for example the number of times the brake is actuated, with a high number indicating a low override intention on the part of the driver. The reaction time until the first braking action can also be taken into account, with the driver's override intention increasing as the reaction time increases. The maximum brake pressure can also be used, in which case there is a negative correlation with the override intention. When taking into account the reaction time until the maximum brake pressure is reached within the period under consideration in which an autonomous braking intervention takes place, the longer the reaction time, the more likely it is that there is an override intention.

Another criterion is the brake pressure integrated over the time of the autonomous braking intervention, whereby an increasing value of the integral indicates a lower override intention.

Furthermore, various state variables relating to the steering angle can be taken into account. For example, it is possible to use the maximum, absolute steering angle deflection in relation to the steering wheel starting position at the start of the autonomous braking intervention as a termination criterion, with increasing steering angle deflection indicating a greater override intention. The dispersion of the steering angle in the intervention period under consideration can also be taken into account as a criterion, since the dispersion represents a measure of the driver's activity, with increasing dispersion indicating a greater override intention.

The steering angle speed also represents a measure of the driver’s override intention.

This non-exhaustive list of different criteria can be taken into account in the blocks 1 to 3 shown or, if the blocks are expanded accordingly, in the method according to the invention, whereby both a cumulative and an alternative combination of different criteria come into consideration, in which subsets from the totality of all criteria are also to be combined cumulatively or alternatively.

$$P>0.5\Rightarrow L=1$$

$$P\le 0.5\Rightarrow L=0$$

durchgeführt, wobei P einen Wahrscheinlichkeitswert für die Erkennung der Überstimmungsabsicht darstellt, der mit einem Schwellenwert verglichen wird, welcher im dargestellten Ausführungsbeispiel bei 0.5 liegt. Die Variablen x₁ bis x_k repräsentieren verschiedene Fahrerreaktionen, beispielsweise manuelle Bremseingriffe, Gaspedalbetätigungen oder Lenkwinkelbetätigungen, bei bo bis b_k handelt es sich um Konstanten. Über die jeweiligen Konstanten bo bis b_k kann eine Gewichtung der verschiedenen Merkmale durchgeführt werden.In the next block 4, at least two signals from the previous blocks 1 to 3, which relate to the driver's operating behavior, are evaluated taking into account a specific calculation rule. Various evaluation rules come into consideration here. For example, a linear combination of several characteristics of the operating behavior can be carried out, whereby the linear combination is transformed into a probability value according to the logistic regression method, the level of which represents a measure of the driver's override intention. The transformation of the linear combination is carried out according to $$P=\frac{1}{1+\text{ex}\left(-\left(b_0+{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="DE102008044214B4\_0006.png"\; state="\{\{state\}\}">b</figure-callout>}}_1\cdot x_1+{\mathrm{<figure-callout\; id="2"\; label="b"\; filenames="DE102008044214B4\_0006.png"\; state="\{\{state\}\}">b</figure-callout>}}_2\cdot x_2+\dots b_k\cdot x_k\right)\right)}$$

$$P>0.5\Rightarrow L=1$$

$$P\le 0.5\Rightarrow L=0$$

carried out, where P represents a probability value for the detection of the override intention, which is compared with a threshold value, which in the illustrated embodiment is 0.5. The variables x ₁ to x _k represent various driver reactions, for example manual braking interventions, accelerator pedal operations or steering angle operations, bo to b _k are constants. The various features can be weighted using the respective constants bo to b _k .

If P exceeds the threshold value, a logical variable L is set to the value 1 or "true", otherwise to the value 0 or "false", where the value 1 or "true" means that the driver has an override intention and the autonomous braking intervention should be aborted, and the value 0 or "false" means that the driver's override intention cannot be determined with sufficient probability, so that the autonomous braking intervention is continued. This transformation is carried out in block 5.

$$\left(x_1<k_1\cap x_2<k_2\cap \dots x_k\ge k_k\right)\Rightarrow L=0$$

According to a further embodiment, the override intention is determined based on concrete threshold values that are assigned to the individual characteristics of the operating behavior, which can be formulated according to the following context: $$\left(x_1\ge {\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="DE102008044214B4\_0006.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\cup x_2\ge {\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="DE102008044214B4\_0006.png"\; state="\{\{state\}\}">k</figure-callout>}}_2\cup \dots x_k<k_k\right)\Rightarrow L=1$$

$$\left(x_1<{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="DE102008044214B4\_0006.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\cap x_2<{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="DE102008044214B4\_0006.png"\; state="\{\{state\}\}">k</figure-callout>}}_2\cap \dots x_k\ge k_k\right)\Rightarrow L=0$$

Here, the variables x ₁ to x _k represent, as in the previous embodiment, the various features of the driver's operating behavior, and k ₁ to k _k represent respectively assigned constants. As can be seen from the first relationship mentioned, in order to recognize an override intention (L = 1), the individual features x ₁ to x _k of the operating behavior must reach the respectively assigned threshold values k ₁ to k _k in a prescribed manner, and in an alternative manner, so that an override intention can be assumed if one of the features reaches the assigned threshold value. Conversely, there is no override intention (L = 0) if the features x ₁ to x _k do not cumulatively reach the respectively assigned threshold value k ₁ to k _k .

After the driver's override intention has been determined using the logical variable L, an additional verification of the driver's action is carried out in the next block 6, which is optional. This ensures that a detected override intention only leads to the shutdown of the autonomous braking intervention if an additional plausibility criterion is met, for example the actuation of the accelerator pedal in order to ensure the intuitiveness of the to improve system response. The driver can then attribute the shutdown of the autonomous braking process to his own actions.

Finally, in the last block 7, the autonomous braking intervention is aborted if the driver's intention to override has been detected; otherwise, the autonomous braking intervention is continued until another termination criterion is met, for example until the vehicle comes to a standstill.

Claims (16)

Method for adjusting a braking system in a vehicle, in which braking force is automatically generated in defined driving situations, wherein the automatic generation of braking force is aborted by a defined driver reaction, wherein the automatic generation of braking force is aborted when at least one driver reaction reaches an associated threshold value, characterized in that the reaction time, the duration, strength and/or number of a driver reaction is taken into account. Procedure according to Claim 1 , characterized in that the automatic build-up of braking force is aborted if at least two defined driver reactions occur. Procedure according to Claim 2 , characterized in that two different driver reactions are taken into account. Procedure according to Claim 2 or 3 , characterized in that two identical driver reactions are taken into account at different times within the time interval in which braking force is automatically generated. Method according to one of the Claims 2 until 4 , characterized in that a characteristic value representing the decision to terminate the automatic generation of braking force is determined from at least two driver reactions in accordance with a predetermined formula. Method according to one of the Claims 2 until 5 , characterized in that the threshold value associated with a driver reaction is determined as a function of two different driver reactions. Method according to one of the Claims 2 until 6 , characterized in that the automatic build-up of braking force is aborted if the at least two driver reactions each satisfy an associated threshold value. Procedure according to Claim 7 , characterized in that the at least two driver reactions are combined linearly. Procedure according to Claim 8 , characterized in that a probability value is determined from the linear combination of the driver reactions, which is used for the decision to abort the automatic generation of braking force. Method according to one of the Claims 7 until 9 , characterized in that the automatic generation of braking force is aborted if at least two driver reactions each exceed an associated threshold value. Method according to one of the Claims 1 until 10 , characterized in that the accelerator pedal operation is taken into account as the driver reaction. Method according to one of the Claims 1 until 11 , characterized in that the steering wheel operation is taken into account as the driver reaction. Method according to one of the Claims 1 until 12 , characterized in that the brake pedal operation is taken into account as the driver reaction. Method according to one of the Claims 1 until 13 , characterized in that a detected override intention only leads to the deactivation of the autonomous braking intervention if a plausibility criterion is met as an additional criterion, for example the actuation of the accelerator pedal. Control device for carrying out the method according to one of the Claims 1 until 14 . Vehicle with a control unit according to Claim 15 .

Images